var canvas = document.getElementById("acanvas");

var w = canvas.width = 200;
var h = canvas.height = 200;

var context = canvas.getContext("2d");

for(i=0;i<w;i++) {
    for(j=0;j<h;j++) {
        var num = Math.floor(Math.random()*255);
        context.fillStyle = "rgb(" + num + "," + num + "," + num + ")";
        context.fillRect(i, j, 0.1, 1);
    }
}

$("#adiv").css ( {
    "background": "url("+canvas.toDataURL()+")"
});